Matching COMMUNITY with Community Lists

Cisco originally created communities as a proprietary feature, treating the 32-bit COMMUNITY as a decimal value (as shown in Example 13-11). When the COMMUNITY PA was added to the BGP standard RFC 1997, the 32-bit COMMUNITY was formatted as AA:NN, where AA is a 16- bit number to potentially represent an ASN, and NN represents a value as set by that ASN. However, the COMMUNITY PA remained a 32-bit number. Cisco routers can use either the original format or the RFC 1997 forma..

CIDR, Private Addresses, and NAT

The sky was falling in the early 1990s in that the commercialization of the Internet was rapidly depleting the IP Version 4 address space. Also, Internet routers’ routing tables were doubling annually (at least). Without some changes, the incredible growth of the Internet in the 1990s would have been stifled. To solve the problems associated with this rapid growth, several short-term solutions were created, as well as an ultimate long-term solution. The short-term solution..

Packet-Switching Links: Frame Relay

Frame Relay was initially developed by the American National Standards Institute (ANSI) in 1984. Cisco Systems undertook major redevelopment of Frame Relay in 1990. StrataCom (now part of Cisco Systems), Northern Telecom, and Digital Equipment Corporation formed a consortium to focus on the development of Frame Relay technology. This consortium developed some additional features for the internetworking environment.   Frame Relay is a packet-switching technology th..

Port-Based Authentication

Catalyst switches can support port-based authentication, a combination of AAA authentication and port security. This feature is based on the IEEE 802.1x standard. When it is enabled, a switch port will not pass any traffic until a user has authenticated with the switch. If the authentication is successful, the user can use the port normally.   For port-based authentication, both the switch and the end user’s PC must support the 802.1x standard, using the Extensible Aut..

Using STUN

STUN provides the ability to emulate an SDLC circuit through an IP network. To simply connect two SDLC or two HDLC ports on different routers, you can use the following: Stun-A#configure terminal Enter configuration commands, one per line.  End with CNTL/Z. Stun-A(config)#interface Loopback0 Stun-A(config-if)#ip address 10.1.15.5 255.255.255.252 Stun-A(config-if)#exit Stun-A(config)#stun peer-name 10.1.15.5 Stun-A(config)#stun protocol-group 1 basic Stun-A(config)#inter..